Fluorescent lamp units that are specially constructed for use in conventional lighting fixtures having screw-type sockets are well known in the art. A lamp unit of this type having a triple-U-bend fluorescent lamp that is mounted on a base structure along with circuit means and is protected by a cover or jacket component is disclosed in U.S Pat. No. 4,270,071, which issued to Morton on May 26, 1981. The convoluted fluorescent lamp is directly wired to the circuit components or the base member of the unit. As a result, the entire unit is discarded upon failure of the fluorescent lamp or one of the circuit components.
From the standpoint of the consumer, it is very advantageous financially to be able to remove and replace only the convoluted fluorescent lamp component of the lamp unit and retain the base structure, protective jacket and circuit components as permanent parts of the light fixture in which the lamp unit is used. A lamp unit of this type is disclosed in U.S. Pat. No. 4,375,607, which issued to Morton et al on Mar. 1, 1983. The cover is releasably fastened to the lower module and can be detached and removed from the unit along with the fluorescent lamp and the ballast component. A pair of tongue-like elements mate with a slotted rim portion of the module. The convoluted fluorescent lamp includes a lamp base having pin terminals which mate with a plug-in socket which allows removal of the lamp.
U.S. Pat. No. 4,503,360, which issued to Bedel on Mar. 5, 1985, discloses another fluorescent unit in which the lamp can be removed from the unit. In the embodiment illustrated in FIG. 9, a pair of tab-like extensions 62 on opposite sides of the cover extend into the associated pair of air ducts and snap interlock with slots provided at the ends of the outer face of the ducts. In an alternative embodiment as shown in FIG. 24, air ducts are formed as integral parts of the cover and are shaped and located so that they register with the port openings in the flange of the module when these components are fitted together in assembled relationship.
U.S. Pat. No. 4,688,874, which issued to Bjorkman on Aug. 25, 1987, describes an adapter for a fluorescent lamp wherein attachment means 26 (in FIG. 9) are provided for the attachment of the cover to the lamp holder.
While the prior art lamp assemblies are satisfactory from the standpoint of providing a compact fluorescent lamp unit that can be used in incandescent-type lamp sockets and fixtures, the construction of the jacket, and more particularly, the means for attaching the jacket is such that it is often difficult to remove the jacket from the lamp unit. Some of the units may be unsuitable for certain fixture location because the jacket allows dirt and moisture to enter. Moreover, some of the units with detachable covers are attached to the lower portion of the unit in a manner which provides a loose fit which may permit undesirable movement of the cover.